Okan Dogu,1 Elan D. Louis,2,3,4,5 Lulufer Tamer,6 Ozgur Unal,1 Arda Yilmaz,1 and Hakan Kaleagasi1
1Department of Neurology, Faculty of Medicine, Mersin University, Mersin, Turkey; 2G.H. Sergievsky Center, 3Department of Neurology, and 4Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, New York, USA; 5Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA; 6Department of Biochemistry, Faculty of Medicine, Mersin University, Mersin, Turkey
Abstract
Background: Essential tremor (ET) is one of the most common neurologic disorders. Aside from underlying susceptibility genes, recent studies have also begun to focus on environmental toxic factors. Yet there remains a paucity of information on such factors, making studies of environmental factors important. A recent study in New York City found blood lead concentrations to be elevated in ET cases compared with matched controls. Chronic exposure to lead produces cerebellar damage, and this could predispose individuals to develop ET.
Objective: The aim of this study was to determine whether the elevation in blood lead concentrations observed in a single study in New York was similarly present in ET cases sampled from a completely different geographic region.
Methods: Blood lead concentrations were measured in 105 ET cases and 105 controls at Mersin University, Mersin, Turkey.
Results: The median blood lead concentration was 2.7 µg/dL in ET cases compared with 1.5 µg/dL in controls (p < 0.001) . In an unadjusted logistic regression model, blood lead concentration was associated with diagnosis: odds ratio (OR) = 4.01 ; 95% confidence interval (CI) , 2.53–6.37 ; p < 0.001 (i.e., each 1-µg/dL increase in blood lead concentration was associated with a 4-fold increased odds of ET) . This association was more robust when cases were compared with a subsample of controls who did not share the same home environment (OR = 8.13 ; 95% CI, 3.05–21.65 ; p < 0.001) . In adjusted models, results were similar.
Conclusions: These data replicate those of a previous study in New York and demonstrate an association between the environmental toxicant lead and a common neurologic disorder.
Key words: epidemiology, essential tremor, etiology, lead, neurology, toxicants. Environ Health Perspect 115:1564–1568 (2007) . doi:10.1289/ehp.10352 available via http://dx.doi.org/ [Online 1 August 2007]
Environmental Health Perspectives Volume 115, Number 11, November 2007
http://www.ehponline.org/docs/2007/10352/abstract.html
